In a medium bowl, combine the pineapple juice, packed light brown sugar, ketchup, reduced-sodium soy sauce, chicken broth, minced fresh ginger, and minced garlic.
Whisk until the brown sugar is dissolved and the marinade is fully combined.
Reserve 1 cup of the marinade for basting.
Cover the reserved marinade and refrigerate it until ready to use.
Divide the remaining marinade evenly between two large resealable plastic bags.
Add 12 chicken thighs to each bag.
Seal the bags securely and turn them several times to coat the chicken evenly with the marinade.
Refrigerate the chicken for at least 6 hours, or overnight for best flavor.
When ready to cook, remove the chicken from the marinade.
Discard the used marinade that has been in contact with the raw chicken.
Moisten a paper towel with cooking oil.
Using long-handled tongs, lightly coat the grill rack with the oiled paper towel to help prevent sticking.
Preheat the grill to medium heat.
Place the chicken on the prepared grill rack.
Cover and grill for 6 to 8 minutes per side, or until the chicken is cooked through.
During the last 5 minutes of grilling, baste the chicken occasionally with the reserved marinade.
Continue grilling until the internal temperature of the chicken reaches 165°F when measured with a meat thermometer.
Remove the chicken from the grill.
Allow the chicken to rest for several minutes before serving.
Serve warm with desired side dishes.